Swivel connectors for connecting pneumatic tools to high pressure air hoses are known. One such connector is described in US Publication No. 2009/0146416 A1 to Chung-Chih Wei. That connector utilizes a ball bearing mechanism to rotatably connect female and male banjo-like parts together.
A disadvantage of that connector is that the female and male parts can lock up during operation (ie. when placed under high pressure) as they are under lateral load. Also, since the source of air can contain moisture, the ball bearing mechanism can rust and seize up.
Yet another disadvantage of that connector is that it utilizes a locking screw/pin and circlip for locking the parts together. Hence it can be tedious to assemble and disassemble.